Lamp assembly

ABSTRACT

A lamp assembly for use with an arc discharge type lamp employing an external trigger wire to provide the required conductive field to establish threshold voltage for initiating current through the lamp.

United States Patent [191 Kidd [451 Feb. 25, 1975 LAMP ASSEMBLY [75]Inventor: Wayne L. Kidd, Fairport, NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

221 Filed: May 29,1973

211 App]. No.2 364,446

[52] U.S. Cl 355/67, 240/l.3, 240/41 R [5]] Int. Cl. G03b 27/54 [58]Field of Search 240/41 R, 41.35 R, 1.3;

[56] References Cited UNITED STATES PATENTS 3,692,994 9/1972 Hirschmanet al 355/67 X Primary ExaminerRichard M. Sheer [57] ABSTRACT A lampassembly for use with an arc discharge type lamp employing an externaltrigger wire to provide the required conductive field to establishthreshold voltage for initiating current through the lamp.

3 Claims, 3 Drawing Figures PATEHTEU FEB 2 5 m5 SHEET 1 0F 2PATEFJTEDFEBZWT? sum 2 85 3 FIG 3 LAMP ASSEMBLY BACKGROUND OF THEINVENTION In xerographic copy machines it has been the practice toilluminate the document to be copied by use of florescent lamps andutilize a scanning system to project reflected rays from the documentonto a moving photoreceptive surface to provide a latent image thereonin conformity with the image on the document.

In order to provide higher speed copiers, the scanning speed and therate of movement of the photoreceptive surface has been increased.However, there is a practical limit to the speed at which the mechanicalcomponents of the scanning system may be operated. For high speedcopying therefor, a xerographic machine having a belt typephotoreceptive surface adapted for flash exposure may be employed toobviate the need for a scanning system. Due-to the operating speed ofthe machine, the illumination system must be capable of providingintense uniform illumination of the document at extremely shortintervals.

This may be accomplished by using lamps of the xenon arc discharge type.To allow rapid flashing of a xenon flash tube, a voltage may be providedacross the flash tube just below the voltage level necessary toestablish conduction therethrough. A trigger wire may be placed alongside the tube, ordinarily by wrapping the tube with the wire. Voltageprovidedto this wire will produce a conductive field along side the tubeto ionize the xenon gas therein, allowing the applied voltage to exceedthe threshold voltage and flash the tube. For proper illumination of thedocument, the tube may be utilized with suitable reflectors.

SUMMARY OF THE INVENTION This invention relates to a lamp assembly forilluminating a document to be reproduced on a reproduction machineincluding a reflector having tubular lamp means spaced therefrom forflash illuminating the document to produce a latent electrostatic imageof the document on a photoconductive surface in the reproductionmachine. Clamp means are mounted on the reflector for releasablysecuring the lamp means in spaced relation to the reflector, the clampmeans being adapted to maintain a flash triggering wire parallel to andadjacent to lamp means in spaced relation from the reflector to preventarcing from the wire to the reflector.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional viewofa xerographic reproduction machine employing the lamp assembly of thepresent invention;

FIG. 2 is a perspective view of an assembled lamp assembly; and,

FIG. 3 is an end view of the lamp assembly of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT For a general understanding ofan electrostatic processing system in which the invention may beincorporated, reference is had to FIG. 1 in which various components ofthe system are schematically illustrated. As in all electrostaticsystems such as a xerographic machine, a light image of an original tobe reproduced is projected on to the sensitized surface of a xerographicplate to form an electrostatic latent image thereon. Thereafter, thelatent image is developed with an oppositely charged developing materialcomprising carrier beads and smaller toner particles triboelectricallyadhering thereto to form a xerographic powder image corresponding to thelatent image on the plate surface. The powder image is thenelectrostatically transferred to a support surface to which it may befixed by a fusing device whereby the powder image is caused permanentlyto adhere to the support surface.

In the illustrated machine, an original D to be copied is placed upon atransparent support platen P fixedly arranged in an illuminationassembly generally indicated by the reference numeral 10. While upon theplaten the illumination system flashes light rays upon the originalthereby producing image rays corresponding to the informational areas onthe original. The image rays are projected by means of an optical system11 to an exposure station A for exposing the photosensitive surface ofamoving xerographic plate in the form of a flexible photoconductive belt12. In moving in the direction indicated by the arrow, prior to reachingthe exposure station A, that portion of the belt being exposed wouldhave been uniformly charged by a corona device 13 located at a belt runextending between belt supporting rollers 14 and 15. The exposurestation extends between the roller 14 and a third support roller 16.

The exposure of the belt surface to the light image discharges thephotoconductive layer in the areas struck by light, whereby thereremains on the belt a latent electrostatic image in image configurationcorresponding to the light image projected from the original on thesupport platen. As the belt surface continues its movement, theelectrostatic image passes around roller 16 and through a developingstation E located at a third run of the belt wherein there is positioneda developing apparatus generally indicated by the reference numeral 17.The developing apparatus 17 comprises a plurality of brushes which carrydeveloping material to the adjacent surface of the upwardly movinginclined photoconductive belt 12 in order to provide development of theelectrostatic image.

The developed electrostatic image is transported by the belt 12 to atransfer station C located at a point of tangency on the belt as itmoves around roller 15 whereat a sheet of copy paper is moved at a speedin synchronism with the moving belt in order to accomplish transfer ofthe developed image. There is provided at this station a transfer roller18 which is arranged on the frame of the machine for contacting thenon-transfer side of each sheet of copy paper as the same is broughtinto transfer engagement with the belt 12. The roller 18 is electricallybiased with sufficient voltage so that the developed image on the belt12 may be electrostatically transferred to the adjacent side of a sheetof paper as the same is brought into contact therewith.

There is also provided a suitable sheet transport mechanism adapted totransport sheets of paper seriatim from paper handling mechanisms 20 and21 to the developed image on the belt as the same is carried around theroller 15. A programming device (not shown) operatively connected to thepaper handling mechanisms and the illumination device is effective topresent a developed image at the transfer station C in timed sequencewith the arrival of a sheet of paper.

After the sheet is stripped from the belt 12 it is conveyed by thestripper transport 23 into a fuser assembly generally indicated by thereference numeral 24- wherein the developed and transferred xerographicpowder image on the sheet is permanently affixed thereto. After fusing,the finished copy is discharged from the apparatus at a suitable pointfor collection externally of the apparatus. The toner particlesremaining as residue on the developed images, background particles, andthose particles otherwise not transferred are carried by the belt 12 toa cleaning apparatus positioned on the run of the belt between rollers14 and adjacent the charging device 13. The cleaning device comprises acorotron 27 for neutralizing charges remaining on the particles and arotating brush 28 for removing the neutralized toner particles from thebelt.

Referring now to FIGS. 2 and 3 there is illustrated one of thereflector-lamp assemblies utilized in the illumination system of themachine. The lamp 30, which is preferably a xenon flash tube, is mountedin spaced relation to a suitable reflector 31 to provide intense, evenillumination of the document on the platen P. For a more completedescription of the relationship be tween the lamps, the reflectors, andthe platen P to provide optimum illumination of the document, referencemay be had to US. Patent Application Ser. No. 270,750, filed July 11,1972, now US. Pat. No. 3,777,135, granted Dec. 4, i973.

The tube is held in the proper spaced position relative to the reflectorby suitable clamps 32 which may be secured to the reflector by means ofself-tapping screws 34. Tabs 36, conforming to the curvature of the tube30, are provided on clamp 32, preferably by being molded thereon toresiliently hold tube 30 in clamp 32.

In order to locate the trigger wire 42 adjacent the tube, a small notch44 is provided near the base of one of the tabs 36. on each clamp. Thetrigger wire is secured to the clamp by suitable means such as screw 38,looped around tab 36 where it is retained in position by notch 44 andstretched along the surface of the tube 30 to the opposite end of thetube where an identical clamp is provided for mounting the opposite endof the tube and the wire.

It can be seen by reference to FIG. 3 that the tube is mounted withinthe reflector 30 in a position which is offset from the axis of thecurved portion of the bottom of the reflector. The disclosed arrangementpositions the trigger wire along side the tube at a location on the tubeto provide the maximum distance possible between the trigger wire andthe reflector to prevent arcing between the trigger wire and thereflector.

The reflector-clamp assembly provides a means for mounting the tube inrelation to the reflector while allowing the end portions of the tube toextend beyond the reflector and clamp for adequate cooling thereof andto prevent excess transmission of heat to the clamp. Also, by extendingthe tube beyond the clamp, the possibility of arcing from the electricalconnections at the ends of the tube to the reflector or clamp isminimized. To further reduce the possibility of arcing either from thetrigger wire or the electrical connectors on the ends of the flash tube,a depending flange 46 is formed on the clamps to increase the arc pathdistance be tween the connections and the end and lower portions of thereflector. Suitable electrical connectors 50 are 5 provided forconnecting the ends of the tube to a suitable source of electrical power(not shown).

The trigger voltage is supplied to trigger wire 42 by suitable wires(not shown) which may be connected to screws 38.

From the foregoing it can be seen that the lamp assembly heretoforedescribed accurately positions the tube relative to the reflector,positions the trigger wire at an optimum location relative to the tubeand the reflector to prevent arcing to the reflector when voltage issupplied to the wire for triggering the tube, allows mounting of thetube such that the heat generated at the electrical connectors theretois not transmitted to the clamp or reflector assemblies, and minimizesthe possibility of arcing between the electrical connections and thereflector or clamps.

While I have described a preferred embodiment of my invention it is tobe understood that the invention is not limited thereto but may beotherwise embodied within the scope of the following claims:

What is claimed is:

l. A lampassembly for flash illuminating a document to be reproduced ona xerographic machine comprising:

a reflector;

dielectric clamp means provided at each end of said reflector forengagement therewith, said clamp means including resilient lamp tuberetaining means,

a tubular lamp, having electrical contact surfaces at each end thereofsaid tubular lamp being retained in said clamp means, in a predeterminedposition relative to said reflector by said resilient means, the ends ofsaid lamp extending beyond said clamp means, said lamp being adapted forconnection at each end thereof to a source of electrical power, theelectrical contact surfaces of said lamp being spaced from said clampmeans and said reflector to prevent arcing therebetween; and,

a trigger wire positioned along side said lamp parallel to the axisthereof, said wire being located and retained against said tubular lampbetween said resilient means and said lamp.

2. A lamp assembly according to claim 1 wherein said lamp is mountedasymmetrically relative to said reflector, said trigger wire beingpositioned on the side of said lamp furthest from said reflector.

3. A lamp assembly according to claim 2, wherein each of said clampmeans is provided with a depending flange formed thereon extending belowthe lower surface of said reflector ,to provide a dielectric shield onthe end of said reflector and thereby increase the arc path distancebetween said trigger wire and the electrical contact surfaces and saidtubular lamp and the end portions of said reflector.

1. A lamp assembly for flash illuminating a document to be reproduced on a xerographic machine comprising: a reflector; dielectric clamp means provided at each end of said reflector for engagement therewith, said clamp means including resilient lamp tube retaining means, a tubular lamp, having electrical contact surfaces at each end thereof said tubular lamp being retained in said clamp means, in a predetermined position relative to said reflector by said reSilient means, the ends of said lamp extending beyond said clamp means, said lamp being adapted for connection at each end thereof to a source of electrical power, the electrical contact surfaces of said lamp being spaced from said clamp means and said reflector to prevent arcing therebetween; and, a trigger wire positioned along side said lamp parallel to the axis thereof, said wire being located and retained against said tubular lamp between said resilient means and said lamp.
 2. A lamp assembly according to claim 1 wherein said lamp is mounted asymmetrically relative to said reflector, said trigger wire being positioned on the side of said lamp furthest from said reflector.
 3. A lamp assembly according to claim 2, wherein each of said clamp means is provided with a depending flange formed thereon extending below the lower surface of said reflector to provide a dielectric shield on the end of said reflector and thereby increase the arc path distance between said trigger wire and the electrical contact surfaces and said tubular lamp and the end portions of said reflector. 